JPH0525287B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a mechanical device such as an industrial robot incorporating a rotary encoder, and a power supply monitor circuit that detects when the power supply is momentarily cut off. This article relates to a rotary encoder with a built-in power supply monitor circuit.

"Prior Art" Generally, in mechanical equipment that incorporates a rotary encoder to perform position control, it is easy to recognize when the power is cut off for a relatively long time, and the output data of the rotary encoder is destroyed as a result of this power cutoff. The matter had been dealt with.

``Problem to be solved by the invention'' However, in the mechanical device incorporating the conventional rotary encoder described above, even if the power is momentarily cut off and the output data of the rotary encoder is destroyed as a result, this can be recognized. This caused problems in terms of accuracy and safety of the mechanical equipment.

This invention was made against this background, and provides a power supply monitor circuit that can detect when the power supply of a rotary encoder is instantaneously cut off, and a rotary encoder incorporating this power supply monitor circuit. The purpose is to provide.

"Means for Solving the Problem" In order to solve the above problem, a first invention provides a pulse whose input end is connected to a power source of a rotary encoder, and which generates a pulse when the voltage at the input end falls below a certain level. a generation circuit, a flip-flop that is preset by the output pulse of the pulse generation circuit to output a power abnormality signal, and is reset by the zero point detection signal of the rotary encoder to cancel the power abnormality signal; It is characterized by consisting of a capacitor that temporarily maintains the power supply.
Moreover, the second invention is characterized in that the power supply monitor circuit of the first invention is built into a rotary encoder.

"Operation" According to the above configuration, when the power supply to the rotary encoder is instantaneously cut off, a pulse is output from the pulse generation circuit, this pulse presets the flip-flop, and the flip-flop issues a power failure signal. . Then, the rotary encoder detects the zero point and issues a zero point detection signal,
When this resets the flip-flop, the power failure signal turns OFF.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a rotary encoder using a power supply monitor circuit according to an embodiment of the present invention. In this figure, 15 is a magnetic scale, which is constructed by magnetizing a predetermined orbit with a sine wave of a constant period. The scale 15 of this embodiment is constructed by setting a circular orbit on the surface of a disk-shaped magnetic material and magnetizing this circular orbit. Further, the wavelength λ of the sine wave used for magnetization is set to about several tens to several hundreds of μm. Magnetic sensors 16 and 17 output level signals corresponding to the strength of magnetization on the magnetic scale 15. Further, the magnetic sensor 17 is set to be shifted by 1/4λ (90°) with respect to the magnetic sensor 16. Therefore, the distance between the magnetic sensors 16 and 17 is (m±1/4)
λ (where m is an integer). The magnetic sensors 16, 17 and the magnetic scale 15 are relatively movable, so that if one of them is fixed, the other rotates. As can be seen from the above, the signal output by the magnetic sensor 16 is
If it is a sine wave, the signal output by the magnetic sensor 17 will be a cosine wave. Therefore, the interval of one period of the magnetization sine wave (from pole to pole of the magnetic scale 15) is θ=
If 0 to 2π, the output signals of the magnetic sensors 16 and 17 will be sin θ and cos θ, respectively.

Next, 18 and 19 shown in FIG. 1 are A/D converters that convert the output signals of the magnetic sensors 16 and 17 into digital signals, respectively, and the digitized sinθ
and cos θ are supplied to one input terminal of digital multipliers 20 and 21. The output signals of the multipliers 20 and 21 are supplied to one and the other input terminals of a digital subtracter 22, respectively, and the output signal of the subtracter 22 is supplied to a digital comparator 23. If the subtraction result of the subtracter 22 is positive, this digital comparator 23
An up pulse is supplied to the counter 24 (8 to 10 bit counter), and if the subtraction result is negative, a down pulse is supplied to the counter 24. 25 is a function generation ROM, and the count value Φ of the counter 24
This outputs sine and cosine data corresponding to . That is, data of sinΦ and cosΦ is stored in advance in the function generation ROM 25,
This stored data is read out sequentially according to the count value Φ. Then, the data cosΦ is supplied to the other input terminal of the digital multiplier 20, and the digital sinΦ is supplied to the digital multiplier 21.
is supplied to the other input end of the . According to the above configuration, the output of the subtracter 22 becomes sin(θ−Φ). Therefore, the comparator 23 outputs an up pulse when the value of sin (θ-Φ) is positive, and a down pulse when it is negative, and as a result, the count value Φ of the counter 24 is
It increases or decreases depending on the value of sin(θ−Φ). In addition, in the above configuration, the multipliers 20 and 21 and the function generation ROM
25 constitutes a function generation multiplier 28, and the comparator 2
3 and the counter 24 constitute a counting means 29. Next, 26 shown in FIG. 1 is a speed detection section that differentiates the output signal Φ of the counter 24 with respect to time t and outputs the result.

Next, 30 and 31 shown in FIG. 1 are waveform shaping devices that convert the output signals of the magnetic sensors 16 and 17, respectively, into binary signals of "H" and "L" by determining them with a predetermined threshold value. It is a circuit. In this case, the output signals P ₁ and P ₂ of the waveform shaping circuits 30 and 31 become rectangular waves whose phases are shifted by π/4, and when the magnetic sensors 16 and 17 move in the positive direction, the output signals P 1 and P 2 become pulse waves.
If P ₁ advances and the movement is in the negative direction, pulse P ₂ advances. 33 is a magnetic sensor 16,
17 is a direction discrimination circuit for discriminating the movement direction,
For example, the direction is determined depending on whether the level of the pulse _P2 is "H" or "L" at the rise of the pulse _P1 . The output signal Sw of the direction determining circuit 33 is supplied to the up/down switching terminal of the counter 34 and is also output to the outside. The counter 34 receives the signal Sw
The pulse _P1 is counted while switching up and down by the . In this embodiment, an up count is performed when the magnetic sensors 16 and 17 are moving in the positive direction, and a down count is performed when the magnetic sensors 16 and 17 are moving in the negative direction. Furthermore, each time the magnetic sensors 16 and 17 rotate the magnetic scale 15 once, the zero point signal Sz output at the reference position is taken out by the zero point detection head 44, and becomes the zero point pulse Pz after passing through the waveform shaping circuit 32. This zero point pulse Pz is supplied to the reset terminal R of the counter 34. As a result, the counter 34 is reset each time the magnetic sensors 16, 17 reach the reference position. Therefore, the count value of the counter 34 corresponds to the number of magnetic sections (number of magnetic poles) on the magnetic scale 15 that the magnetic sensors 16, 17 have passed between the current position of the magnetic sensors 16, 17 and the reference position. will be the value. The output signal of the counter 34 and the output signal of the counter 24 become the absolute position data Dout. In this case, the output signal N of the counter 34 constitutes the data of the upper bits of the data Dout, and the count value Φ of the counter 24 constitutes the data of the lower bits of the data Dout. The absolute position data Dout is
The signal is input to the parity check circuit 35. This parity check circuit 35 checks the total number of bits with a value of "1" among all the bits making up the absolute position data Daut, and checks the parity bits so that the odd/even of this total number satisfies a predetermined condition. Add and output externally. At this time, a power abnormality signal AL is output from the power supply monitor circuit 40, which will be described later.
When Dout is "L", a regular parity bit is added, and the absolute position data Dout is used externally as valid data. On the other hand, when the power supply abnormality signal AL is "H", a parity bit that is an inversion of the normal one is added. As a result, a parity error is detected in the subsequent circuit, and the absolute position data Dout is invalidated.

The rotary encoder 10 described above has a built-in power supply monitor circuit 40 described below.
In FIG. 1, 41 is a power supply monitor input terminal, which is connected to the system power supply of the rotary encoder. 51 is a pulse generation circuit whose input terminal is connected to the power supply monitor input terminal 41, and outputs a positive pulse when the input level falls below a certain value. An output terminal of pulse generation circuit 51 is connected to an input terminal of inverter 52. The inverter 52 inverts the output voltage of the pulse generating circuit and outputs it. Further, the anode _of the diode D1 is connected to the power supply monitor input terminal 41. A resistor _R1 whose one end is grounded and the other end of a capacitor _C1 are connected to the cathode of the diode D1, and a D-type flip _- flop 53 is connected to the cathode of the diode D1.
The power supply terminal Vcc, data input terminal D, and clock input terminal C are connected to each other. The D-type flip-flop 53 has a reset input terminal R and a preset input terminal PR, the reset terminal R is connected to the zero point signal input terminal 42, and the preset input terminal PR is connected to the output terminal of the inverter 52. There is. Further, the zero point signal Sz detected by the zero point detection head in the rotary encoder 10 is waveform-shaped by a waveform shaping circuit 45 and supplied to the zero point signal input terminal 42 as a signal _Sz1 . The output terminal Q of the flip-flop 53 is connected to the power supply abnormality signal output terminal 43. The power abnormality signal AL from the power abnormality signal output terminal 43 is supplied to the parity check circuit 35 in the rotary encoder described above.

Next, the operation of this embodiment with the above configuration will be explained.

First, the operation of the rotary encoder 10 will be explained. When the magnetic sensors 16 and 17 move in the positive direction, the counter 34 counts up each time the magnetic sensors 16 and 17 pass through a magnetic section (magnetization pitch), and this count value is output to the upper bit of the data Dout. be done. Therefore, if we look at the upper bits of the data Dout, we can see how many magnetization sections the magnetic sensors 16 and 17 have passed through, that is, how many pitches from the reference position the magnetic sensors 16 and 17 are currently located. I understand.

On the other hand, the signals sinΦ and cosΦ output from the magnetic sensors 16 and 17 are transmitted to the A/D converters 18 and 19, respectively.
multiplier 2 after being converted into a digital signal by
0 and 21 are multiplied by the signals cosΦ and sinΦ output by the function generation ROM 25. As a result, the output signals of multipliers 20 and 21 are sinΦcosΦ, respectively.
cosΦsinΦ. Then, these output signals are supplied to the subtracter 22, and the subtracter 22 outputs sin(θ
−Φ) is output. The comparator 23 calculates this sin(θ
-Φ), an up-count pulse or a down-count pulse is supplied to the counter 24. Therefore, the count value Φ of the counter 24 increases when sin(θ-Φ) is positive and decreases when it is negative. And the output of the function generation ROM
Since sinΦ and cosΦ each increase or decrease according to the count value Φ, the circuit shown in FIG.
Φ)=0, that is, a phase-locked loop with Φ=Φ. Therefore, the counter 24
The count value Φ indicates where the magnetic sensor 13 is in the magnetization section, in other words, the count value Φ of the magnetic sensor 16
This is data that shows where the is located between the magnetic poles.

Next, the operation of the power supply monitor circuit 40 will be explained.
FIG. 2 is a time chart showing the operation of the power supply monitor circuit in this embodiment.

At time t ₀ , when the system power is turned on, the output voltage of the pulse generation circuit 51 increases as the system power is turned on. and,
After a certain period of time has passed, the inside of the pulse generating circuit 51 enters a steady state, and its output becomes the "L" level (see time _t1 ). Accordingly, the output of the inverter 52 changes from the "L" level to the "H" level. On the other hand, when the system power supply starts up, the capacitor _C1 is charged from the system power supply side via the diode _D1 , so the power supply voltage Vcc of the flip-flop 53 gradually rises and eventually reaches the "H" level. (see time t ₂ ). The flip-flop 53 is connected to the power supply voltage.
When Vcc reaches the "H" level, it enters a set state and outputs a "H" level signal from its output terminal Q. Output terminal Q, that is, power supply abnormal signal AL
becomes “H” level. As a result, the parity check circuit 35 inverts the sign of the parity bit added to the absolute position data Dout, and henceforth, the absolute position data output from the rotary encoder is treated as invalid.
Here, the zero point positioning of the rotary encoder is performed. For example, at time _t3 , when the zero point alignment of the rotary encoder is completed, a zero point signal Sz is generated, which is input to the reset terminal R of the flip-flop 53 via the waveform shaping circuit 45, and the flip-flop 53 is reset. Ru. As a result, the power supply abnormality signal AL becomes "L" level. As a result, the sign inversion of the parity bit in the parity check circuit 35 is canceled, and henceforth, the absolute position data output by the rotary encoder becomes valid. next,
For example, if the system power supply momentarily fails at time _t4 , a pulse is generated from the pulse generation circuit. At this time, the power supply voltage Vcc of the flip-flop is held by the capacitor _C1 . Therefore, at time _t4 , the flip-flop is preset, and the power supply abnormality signal AL becomes "H" level. As a result, parity check circuit 3
In step 5, the added parity bit is inverted, and the absolute position data output by the rotary encoder is treated as invalid.

"Effects of the Invention" As explained above, according to the present invention, there is provided a pulse generation circuit whose input terminal is connected to a power source of a rotary encoder and which generates a pulse when the voltage at the input terminal falls below a certain level; A flip-flop is preset by the output pulse of the pulse generating circuit to output a power abnormality signal, and is reset by the zero point detection signal of the rotary encoder to cancel the power abnormality signal. Configure a power supply monitor circuit with a capacitor that maintains
Since this power supply monitor circuit is built into the rotary encoder, it is possible to detect an instantaneous power failure in the power supply of the rotary encoder.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a rotary encoder incorporating a power supply monitor circuit according to an embodiment of the present invention, and FIG. 2 is a time chart showing the operation of the power supply monitor circuit according to the embodiment. 51...Pulse generation circuit, 53...Flip-flop, _C1 ...Capacitor, 10...Rotary encoder, 40...Power monitor circuit.

Claims (1)

[Scope of Claims] 1. A pulse generating circuit whose input terminal is connected to the power source of the rotary encoder, and which generates a pulse when the voltage at the input terminal falls below a certain level, and which is preset by the output pulse of the pulse generating circuit. A power supply monitor comprising a flip-flop which outputs a power supply abnormality signal and which is reset by the zero point detection signal of the rotary encoder to cancel the power supply abnormality signal, and a capacitor which temporarily retains the power supply of the flip-flop when the power is cut off. circuit. 2. A rotary encoder incorporating the power supply monitor circuit according to claim 1.